Millimeter Wave Hybrid Photonic Wireless Links for High-Speed Wireless Access and Mobile Fronthaul

As the introduction of the fifth generation of mobile services (5G) is set to revolutionize the way people, devices and machines connect, the changes to the underlying networks and technologies are no less drastic. The massive increase in user and data capacity, as well as the decrease in latency require a complete re-thinking of radio access networks – one important aspect of which is the introduction of millimeter wave communications, which is expected to play a key role.

Millimeter wave hybrid photonic wireless links seamlessly merge the wired optical and wireless radio network segments and combine the best of both technologies, offering very large capacity and bridging long distances with optical fiber, while retaining the flexibility and easy deployment of wireless communications.

The research in this thesis experimentally investigates millimeter wave (mmw) hybrid photonic wireless links, demonstrating their potential and pushing their implementation beyond the state of the art. While touching upon a multitude of aspects, the contributions can mostly be classified in three larger groups: first, the demonstration of mmw radio-over-fiber (rof) links in various configurations of reduced complexity, real-time enabled and almost ready for deployment.

Second, the use of advanced modulation formats to increase the capacity and spectral efficiency of mmw rof links, to enhance their robustness against channel impairments and to allow flexible resource allocation. Therein, a significant increase of spectral efficiency is achieved for rof links in W-band using multi-band carrierless amplitude phase modulation (multicap), the first experimental validation of wavelet coding for robustness against frequency fading is performed, and the combination of multicap with non-orthogonal multiple access for flexible user and resource allocation is suggested and experimentally demonstrated.

Third, the integration of mmw rof links with optical networks and the resulting impact on the design and architecture of the remote station, performing heterodyne up-conversion, is considered, demonstrating real-time transmission with a fully reconfigurable remote station. The thesis further contains work on optical vector network analysis as an efficient tool for the characterization of optical space division multiplexing fibers and components – as a prerequisite for their future use in mmw rof links and radio access networks.

In summary, the work presented in this thesis has regarded a multitude of aspects of millimeter wave hybrid photonic wireless links, expanding upon the state of the art and showing their feasibility for use in fifth generation mobile and high speed wireless access networks – hopefully bringing them a small step closer to adoption in deployed networks.